The silver halide system photography is superior to other photographic processes such as electrophotography and diazo process in sensitivity and gradation adjustment and thus has heretofore been most widely used. In recent years, a technique which can easily and rapidly provide an image has been developed by changing the process for the formation of an image on a light-sensitive material from the wet process with the conventional developer or the like to the dry process by heating or the like.
Many methods for obtaining color images by heat development have been proposed. Methods which comprise the bonding of an oxidation product of a developing agent and a coupler to form a color image have been proposed in U.S. Pat. Nos. 3,531,286, 3,761,270, and 4,021,240, Belgian Patent 802,519, and Research Disclosure (September 1975, page 32).
However, these methods are disadvantageous in that an image of reduced silver and a color image are formed on heat developed exposed portions at the same time, causing stain on the color image.
In order to eliminate this disadvantage, many approaches have been proposed, e.g., method which comprises imagewise form or release a mobile (diffusive) dye by heating, and then transferring the mobile dye to a dye fixing element having a mordant with a solvent such as water or a high boiling organic solvent or a hydrophilic heat solvent incorporated in the dye fixing element and method which comprises transferring a thermally diffusive or sublimable dye to a dye receiving element such as support (U.S. Pat. Nos. 4,463,079, 4,474,867, 4,478,927, 4,507,380, 4,500,626, and 4,483,914, and JP-A-58-149046, JP-A 58-149047, JP-A-59-152440, JP-A-59-154445, JP-A-59-165054, JP-A-59-180548, JP-A-59-168439, JP-A-59 174832, JP-A-59-174833, JP-A-59-174834, and JP-A-59-174835 (the term "JP-A" as used herein means an "unexamined published Japanese patent application")).
In general, if dye fixing elements on which an image has been formed by a transfer process such as the above mentioned image formation methods are kept with their surface on the dye fixing layer side laminated opposed to each other, the dye image is retransferred to the counterpart dye fixing layer. In particular, for the purpose of simplifying development process, it is effective to incorporate a base or base precursor in a light-sensitive element or dye fixing element which is then subjected to heat development to form an image. However, the "contact dye transfer" is worsened. Particularly, in a system where heat develoment and transfer are effected in the presence of a small amount of water, a water-soluble base or base precursor is preferably used. In this case, the "contact dye tranfer" is further worsened.
In order to overcome this difficulty, the inventors previously proposed a dye fixing element comprising a nonionic water-soluble polysaccharide (particularly pullulan and dextran) in JP-A-62-47639 ad a dye fixing element having a protective layer mainly comprising an anionic water-soluble polymer as an outermost layer in JP-A-63-103240.
The above mentioned methods exert remarkable effects on the "contact dye transfer". However, if the light-sensitive material is stored under the circumstances of high humidity for prolonged period of time, its effect is not always sufficient. Thus, further improvements have been desired. A polymer dispersion having a glass transition temperature of 25.degree. C. or lower may be effectively incorporated in a dye fixing layer and/or adjacent layers thereto in a dye fixing element free of back layer as a curl balance layer to improve the curling properties. However, this worsens the "contact dye transfer".
In general, means of inhibiting the "contact dye transfer" causes deterioration of transferability also during the image formation, often resulting in an insufficient transfer density.
On the other hand, if a lamination of a light-sensitive material and a dye fixing material to both or either of which a small amount of water has been supplied is subjected to heat development/transfer process, an uneven image (honeycomb density unevenness) which is attributable to partial contact failure may occur depending on the amount of water supplied and heating condition.
A layer comprising a hydrophilic binder is normally provided on the back layer in a dye fixing element as a curl balance layer. If a lamination of such dye fixing elements is stored under the circumstances of high humidity, a base and/or base precursor contained in the surface layer partially migrates to the back layer, causing unevenness in the distribution of the base or base precursor in the surface layer. As a result, when such a dye fixing element laminated with a light-sensitive element is subjected to development and transfer, it causes unevenness in development and transfer. Accordingly, blank areas are generated in the transferred image.
In order to solve this problem, the inventors previously proposed a dye fixing element comprising in the back layer finely divided grains having a size greater than the thickness of the back layer in JP-A-63-274952.
The above mentioned approach exerts remarkable effects in inhibiting the blank areas from generation. However, if the light-sensitive material is stored under the circumstances of high humidity under pressure for prolonged period of time, its effect is not always sufficient. Thus, further improvements have been desired. In particular, if the light-sensitive material is for use in transmission type, the amount of finely divided grains to be added is limited from the standpoint of transparency (haze). Thus, an approach for inhibiting the blank areas from generation without deteriorating trasnparency has been desired.